However, Ryanair previously insisted that customers could only pay for free if they used Visa Electron, a relatively little-used pre-paid card. It later changed the rules so that only a pre-paid MasterCard would avoid the charges.

Now the change to Ryanair's own branded card - also administered by MasterCard - will bring accusations that the airline is making customers jump through hoops in order to access free payments that the law intends to be easily available.

The Office of Fair Trading has already launched an investigation into airline card charges following a complaint by the consumer organisation Which?